#!/usr/bin/env bash

#
# nagios-downtime(1) -- Shortcut to scheduling fixed downtime in Nagios,
# because it's annoying to do with the web interface for large sets of hosts
# or services.
#
#     $ ndt (<host[/service][,host[/service],...>|-) <start> <end> [comment]\n' "$self"
#
# You can specify multiple objects by separating them with commas:
#
#     $ ndt abc-example-ap-1,abc-example-ap-2/VOLTAGE 9am 10am 'Power problems at abc-example'
#
# Even easier is to pipe them into stdin by specifying - as the object:
#
#     $ nds abc-example | ndt - 9am 10am 'Power problems at abc-example'
#
# Assumes date(1) with +%s format and --date option (probably only GNU date).
#
# Author: Tom Ryder <tom@sanctum.geek.nz>
# Copyright: 2016
#

# Name self
self=nagios-downtime

# Usage printing function
usage() {
    printf 'USAGE: %s [<host[/service][,host[/service],...>|-] <start> <end> [comment]\n' "$self"
}

# Process options (just help at the moment)
OPTIND=1
while getopts 'h' opt ; do
    case "$opt" in
        h)
            usage
            exit 0
            ;;
        '?')
            usage >&2
            exit 1
            ;;
    esac
done
shift "$((OPTIND-1))"

# Bail if too few arguments left; we need at least the hostname, the start date, and the end date
if (($# < 3)) ; then
    usage >&2
    exit 1
fi

# Define relatively fixed/guaranteed fields for Nagios command; note that the
# comment has a default of 'no comment given'
now=$(date +%s)
spec=$1
fixed=1
trigger=0
duration=0
author=${SUDO_USER:-$USER}
comment=${4:-'no comment given'}
cmdfile=${NAGCMD_FILE:-/usr/local/nagios/var/rw/nagios.cmd}

# How to get the objects depends on the spec (the first argument)
declare -a objects
case $spec in

    # If the spec is just "-", we just read unique objects from stdin
    -)
        while read -r object ; do
            [[ $object ]] || continue
            objects[${#objects[@]}]=$object
        done < <(sort -u)
        ;;

    # If the spec is anything else, we break it up with commas and read the
    # objects that way
    *)
        IFS=, read -a objects -r < <(printf '%s\n' "$spec")
        ;;
esac

# There must be at least one object
if ! ((${#objects[@]})) ; then
    printf '%s: At least one host/service must be given\n' \
        "$self" >&2
    exit 1
fi

# All the hosts or services must exist, just to be strict
for object in "${objects[@]}" ; do
    nagios-exists "$object" && continue
    printf '%s: Host/service %s does not seem to exist\n' \
        "$self" "$object" >&2
    exit 1
done

# Attempt to parse start and end dates; fail if the call doesn't work
dta=$(date +%s --date "$2") || exit
dtb=$(date +%s --date "$3") || exit

# If the end time is less than right now, this is probably a mistake
dtn=$(date +%s)
if ((dtn > dtb)) ; then
    printf '%s: Refusing to schedule downtime ending in the past (%s)\n' \
        "$self" "$(date -d @"$dtb" +%c)"
    exit 1
fi

# If the end time is less than the start time, this is definitely a mistake
if ((dta > dtb)) ; then
    printf '%s: Refusing to schedule downtime that ends (%s) before it starts (%s)\n' \
        "$self" "$(date -d @"$dtb" +%c)" "$(date -d @"$dta" +%c)"
    exit 1
fi

# Quietly replace semicolons in comment with commas
comment=${comment//;/,}

# Write commands to schedule downtime for each of the objects, bail if a single
# one of them fails
for object in "${objects[@]}" ; do
    case $object in
        */*)
            host=${object%/*}
            service=${object##*/}
            cmd=$(printf '[%lu] SCHEDULE_SVC_DOWNTIME;%s;%s;%s;%s;%u;%u;%u;%s;%s' \
                "$now" "$host" "$service" "$dta" "$dtb" \
                "$fixed" "$trigger" "$duration" "$author" "$comment")
            ;;
        *)
            host=$object
            cmd=$(printf '[%lu] SCHEDULE_HOST_DOWNTIME;%s;%s;%s;%u;%u;%u;%s;%s' \
                "$now" "$host" "$dta" "$dtb" \
                "$fixed" "$trigger" "$duration" "$author" "$comment")
            ;;
    esac
    printf '%s\n' "$cmd" > "$cmdfile" || exit
done